The present invention pertains to heat exchangers for flowing fluids and, more particularly to a modular heat exchanger in which each of the core modules is formed from a unitary block of a heat exchange material.
Conventional heat exchanger construction of the type particularly adapted for automotive use utilizes heat exchanging core elements which include a series of generally parallel tubular conduits extending between and attached at their opposite ends to inlet and outlet headers. The tubular conduits are typically provided with heat conducting and dissipating fins which may be either of a flat plate or serpentine construction and which are soldered or brazed to the tubular conduits. The conduits, in turn, are also typically soldered or brazed to the headers or to similar fluid accumulating tanks. The rigid soldered or brazed joints have always constituted a common source of heat exchanger failure and, when the heat exchangers are used in automotive applications, repairs usually require removal of the entire radiator and resultant downtime for the automotive equipment. Thus, there has long been a need and desire for a heat exchanger having unitary core elements and one in which brazed or soldered connections can be minimized and, preferably, eliminated completely.
U.S. Pat. No. 3,222,764 discloses various related methods for making unitary finned tubular conduits, suitable for use in heat exchangers, from billets of aluminum or other ductile metals. An aluminum billet with a central through bore is provided with a series of cut grooves on opposite surfaces extending in the direction of the through bore. The billet is then rolled transversely and longitudinally to flatten the ridges forming the grooves and to close the bore. The reduction in thickness of the billet is extreme (to about 1/40 the original billet thickness) and the finned walls originally defining the walls of the cut slots are mechanically peeled back to form a series of parallel upstanding fins. The bore is also reopened to form a unitary finned conduit. Various alternate embodiments of finned tubes are shown, but there is no disclosure of any structure or method for incorporating the same into a modular heat exchanger.
U.S. Pat. No. 3,692,105 also describes a unitary heat exchanger core in which an elongate tubular aluminum member has a series of parallel fins formed thereon by peeling back surface layers in stepwise fashion and turning the peeled layers upwardly to extend perpendicularly from the tubular member. This patent also discloses bending a long section of such a unitary finned tube in a serpentine pattern to form a heat exchanger unit. The construction, however, is not modular.
My own U.S. Pat. Nos. 4,979,560 and 5,042,572 disclose modular heat exchangers of the type having easily replaceable modules and which are suitable for automotive or mobile equipment applications. However, the modules disclosed in these patents are of conventional tube and fin construction or of a corrugated sheet metal construction which require substantial amounts of welding, brazing or soldering to assemble the various components.
In accordance with my co-pending application Ser. No. 08/072,497, filed Jun. 4, 1993, a modular heat exchanger is disclosed which includes unitary finned tubular core elements which can be assembled into a multi-module heat exchanger, including flow distributing headers or end tanks without any brazed, soldered, or welded connections of any kind. The heat exchanger is fully disassemblable in one embodiment, however, mechanical connectors and a substantial number of O-ring seals are required for assembly. In another embodiment, welded or brazed connections may be utilized to provide units which are partially disassemblable. However, these units are potentially subject to the prior art problem of inadequate joint strength and environmentally less desirable materials.